This invention relates to a cam follower in the form of a roller for use in cam and follower mechanisms for operating valves, fuel injection devices, and similar elements such as found in internal combustion engines. In particular, this invention relates to a means in the form of annular grooves of arcuate cross-section located in opposite sides of a roller in order to minimize contact stress.
In prior art cam and follower mechanisms contact stresses are set up along the point of contact between the roller and cam surface. These contact stresses are typically variable and range from a minimum at the roller center to a maximum at the roller edge. The substantial edge loading thus produced, after extended operation, causes wear on the cams and rollers. This is especially true where diesel engines are concerned as when used to operate fuel injectors. Observations made on the worn cam shaft show that in most instances cam wear initiates at the outer edge of the follower roller. Wear then progresses from the point of initiation across the lobe of the cam until the full width of the roller path engagement on the cam surface is encompassed.
In order to mitigate or eliminate such wear, various approaches have been used. One approach is that shown in U.S. Pat. No. 3,831,457 to Kearn. In that construction the outer peripheral contact surface of the cam roller is of varying width to effect a variable roller edge contact on the surface of the cam. However, while the edge loading is caused to variably track across the cam, maximum stresses still occur in the roller edges.